Dust traps are used in gas lines to remove dust particles which otherwise would clog diaphragm-like regulators which are used to reduce the gas pressure between street gas mains and diversions to individual homes.
Dust is caused by residuals from manufacturing gas accumulating inside gas pipes. The problem is aggravated when gas pressure is increased and raises more dust. This happens, for example, when new extensions are added to old gas networks. As a city grows more and more gas pipes are added to the original networks. Gas pressure is then increased through the older pipes in the older part of the city to increase flow. The increased flow will loosen or raise more dust and increase the problem of dust in both the old and new parts of the network.
In the prior art this problem is overcome by inserting a filer bag or sleeve into the gas pipe. The bag is retained on a coil spring held within a bushing having inner and outer threads. The bushing is screwed into a threaded end of the gas pipe. The problems with this solution are that the bushing is relatively expensive and that gas pipe must be provided with an inner thread for holding the bushing. Also, it is difficult to remove the bushing from the pipe since dust will tend to accumulate in the thread grooves, making removal difficult.